In industrial application, it is common that a variety of organic media and water are mixed in a container. Therefore, it is required to measure the net content of the water or organic medium therein. In the petrochemical industry, a typical requirement is used to precisely measure the net content of the crude oil within a crude oil tank containing an oil-water emulsion layer. However, since the medium within the crude oil tank is distributed unevenly, there is not yet a mature technology meeting the above requirement now.
In the related prior art, the patent No. 02110211.2, entitled “multiphase material level sensor”, previously proposed by the inventor of the present application provides a level measuring apparatus capable of qualitatively measuring the oil-water distribution in a crude oil tank. According to the technical solution, it is provided a measuring sensor, which is wrapped by an insulating layer and composed of multiple segment electrodes in the vertical direction. Segment electrodes composing the measuring sensor are independent of each other. A capacitive or impedance sensor is formed by each of the segment electrodes and the wall of the tank, which is referred to as a segment sensor. The medium between a segment electrode and the tank is function as electrolyte of the corresponding segment sensor. Output signals of each of the segment sensors are transported to a signal and data processing unit that is located on the outside of the tank through the respective cable directly or through a data bus after an A/D conversion. The signal and data processing unit determines the property of the medium in the tank according to the property and amplitude of the output signal of the segment sensor corresponding to the medium, thereby obtaining the general distribution of the medium within the tank in the vertical direction.
The problems of the existing technical solutions are as follows, firstly, the apparatus that is provided in the tank meeting the requirement of production or the like, may significantly affect the measuring signal of the segment sensor, thereby affecting the measuring of the medium distribution within the tank by the signal and data processing unit. Secondly, since the distance from the outer surface of a segment electrode to the wall of the tank is far more than the height of the segment electrode in the vertical direction, besides the horizontal medium layer on which the segment sensor is located, horizontal medium layers in a certain distance above and below the horizontal medium layer may affect output signals of the segment sensor. Because the property of each horizontal medium layer within the tank is uncertain, the effect on output signals of the horizontal medium layer generated by the horizontal medium layers above and below the horizontal medium layer is uncertain. In this way, according to the existing technical solution, the distribution in the vertical direction of the multiphase medium including water in a tank can be measured approximately, but the composition, such as the water content, of the medium layer on which the segment sensor is located, can not be measured accurately.